Sensors for converting physical quantities into electrical signals are known in a wide variety of embodiments and structural sizes. If particularly small sensors are required, a realization in the form of a semiconductor device affords advantages. Also, semiconductor sensors can readily be integrated into a circuit periphery that may be situated on the same semiconductor substrate and enables an interconnection of the sensor.
In the case of semiconductor sensors, the active front side of the semiconductor chip often has to be uncovered in order to enable an error-free function if, for example, pressure values, sound oscillations of the air or other physical quantities are intended to be measured. Thus, particularly in the case of pressure sensors or in the case of sound sensors (microphones), it is necessary to ensure the oscillation capability of a diaphragm. The oscillations are then converted into electrical signals.
Other sensors, too, for example, for temperature or for detecting specific gases, require an uncovered sensor surface, under certain circumstances. The same applies to all kinds of optical sensors which can be used as transmitters and receivers. Thus, the optically effective sensor and/or actuator surfaces of laser devices, of LEDs and also of cameras (with a CCD sensor or the like) must enable unimpeded coupling-in and/or coupling-out of signals. In spite of this, high requirements are made of the reliability and, in particular, of the mechanical robustness of semiconductor devices of this type.
For the realization of sensor housings, consideration is given to lead frame technology in which a cavity is provided for the semiconductor chip. Examples thereof are “premolded packages” having a cover or a construction comprising a plurality of parts, which, during assembly, are joined together to form a cavity. In the case of optical housings, the configuration of the device must enable the exact coupling of an optical signal line, for example, of an optical fiber line. For this purpose, relatively complex plug connections outside the device housing, or, if appropriate, coupling/plug devices in the housing are provided.
Semiconductor devices with a pressure sensor and semiconductor devices with an optical sensor and with devices for coupling optical signals in or out are known.
A semiconductor device having a sensor surface and/or actuator surface, which is constructed in a simple manner and which can be produced simply and cost-effectively, and a simple method for producing such a semiconductor device, are desirable.